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Chemistry

Chemistry. Water, Acids and Bases. Inorganic Chemistry. The study of inorganic compounds water acids bases. Water. Chemical formula = H 2 O Properties Cohesive, form H bonds Adhesive, clings to surfaces Polar. Cohesion and Adhesion. sequoias. among water molecules

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Chemistry

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  1. Chemistry Water, Acids and Bases

  2. Inorganic Chemistry • The study of inorganic compounds • water • acids • bases

  3. Water • Chemical formula = H2O • Properties • Cohesive, form H bonds • Adhesive, clings to surfaces • Polar

  4. Cohesion andAdhesion sequoias • among water molecules plays a key role in the transport of water against gravity in plants • clinging of one substance to another, contributes too, as water adheres to the wall of the vessels. wood cut

  5. Surface Tension • a measure of the force necessary to stretch or break the surface of a liquid, is related to cohesion. • Water has a greater surface tension than most other liquids • Water behaves as if covered by an invisible film • Some animals can stand, walk, or run on water without breaking the surface

  6. Polarity of Water • The molecule has opposite charges on opposite sides • polar molecules form H bonds with other polar molecules

  7. Activity • Explain why water sticks to your skin when you take your finger out of the water. • Explain why these leaves float instead of submerging. • Name the property that makes water molecules attach to each other due to its surface charge.

  8. answers Adhesion & cohesion Surface tension Polarity

  9. Water is the Solvent of Life • solution = solvent + solute(s) • ex: cup of coffee • hot water (solvent) • sugar (solute) • coffee grounds (solute) • Aqueous solution • The solvent is water ramsey.k12.nj.us

  10. Water Forms Hydrogen Bonds With Ions • The Na+ cations form hydrogen bonds with partial negative oxygen regions of water molecules. • The Cl- anions form hydrogen bonds with the partial positive hydrogen regions of water molecules. • Hydration shell - each dissolved ion is surrounded by a sphere of water molecules

  11. Polar molecules are also soluble in water. • Even large molecules, like proteins, can dissolve in water if they have ionic and polar regions.

  12. Hydrophilic • any substance that has an affinity for water • Some are water-soluble • water molecules are attracted to molecules with an electrical charge (ionic or polar bonds) • H-bond formation may form

  13. Hydrophobic • Substances that have no affinity for water • Non-ionic & non-polar compounds are repelled by water • Water-insoluble • Hydrophobic molecules are major ingredients of cell membranes • Some vegetables and fruits with non-polar pesticides

  14. Mole concept • Counting individual or even collections of molecules is not practical • Instead, we can use the concept of a mole to convert weight of a substance to the number of molecules in that substance and vice versa

  15. Mole (mol) • Is equal in number to the molecular weight of a substance, but up scaled from daltons to grams • Ex. a mole of sucrose (C12H22O11) • C = 12 daltons x 12 • H = 1 dalton x 22 • O = 16 daltons x 11 • Sucrose molecular weight = 342 daltons • one mole of sucrose = 342 g

  16. Avogradro’s number • The actual number of molecules in a mole 6.023 x 1023 • A mole of sucrose • contains 6.023 x 1023 molecules • weighs 342g

  17. Molarity • the concentration of a material in solution • one molar solution • has one mole of a substance dissolved in one liter of solvent, typically water. • Example: to make a 1 molar (1 M) solution of sucrose add water to 342 g of sucrose until the total volume is 1 liter and all the sugar is dissolved

  18. Ionization of Water • 2 H2O H3O+ + OH- • by convention: H2O H+ + OH- • pH of pure water is 7 (10-7M) + - + hydronium hydroxide

  19. pH • Scale 0-14 • logarithmic scale • pH = - log10 [H+] • acid pH< 7 • base pH>7 • neutral pH = 7 • pure water at RT: pH = -log 10-7M =-(-7) = 7

  20. Neutral Solution • In a neutral solution [H+] = [OH-] = 10-7 M, and the pH = 7. • Values for pH decline as [H+] increase. • While the pH scale is based on [H+], values for [OH-] can be easily calculated from the product relationship • [H+] + [OH-] = 14

  21. Acids • substances that increase [H+] in solution • pH below 7 • ex: HCl H+ + Cl - • acid precipitation, with pH < 5 • acid indigestion use antacids

  22. Bases • substances that reduce [H+] in solution • pH above 7 • NH3 + H+ NH4+ • NaOH Na+ + OH- ammonia ammonium ion sodium hydroxide sodium hydroxyde ion ion

  23. Activity • Rain has a pH of 5. • Is it an acid, base or neutral? • What is the concentration of H ions? • What is the concentration of OH ions?

  24. answers • Rain has a pH of 5. • acid • [H+] = 10-5 M • [OH-] = 10-9 M

  25. Buffer • prevents sudden pH changes in biological fluids • accept hydrogen ions from the solution when they are in excess and donate hydrogen ions when they have been depleted • H2CO3 HCO3- + H+ carbonic acid bicarbonate ion hydrogen (donor of H+) (receptor of H+) (ion) The End

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